It is generally known that dihydroxyacetone, when applied topically to human skin, will produce a tanned appearance, i.e. an artificial tan. U.S. Pat. No. 4,708,865, to Turner, issued Nov. 24, 1987 describes the use of hydro-alcoholic solutions of dihydroxyacetone for tanning the skin; U.S. Pat. No. 4,466,805, to Welters, issued Aug. 21, 1984 describes hair and skin coloring formulations containing dihydroxyacetone; and U.S. Pat. No. 2,949,403, to Andreadis et al., issued Aug. 16, 1960 describes artificial tanning formulations containing dihydroxyacetone in an oleaginous base. However, it is also known that emulsion products containing dihydroxyacetone have a short shelf life, tending to darken and develop disagreeable off-odors over time with a concomitant loss of emulsion integrity. Dihydroxyacetone is relatively sensitive to heat, light, moisture, and alkaline pH. Dihydroxyacetone can react with other ingredients in a formulation, especially with nitrogen-containing compounds, such as amines, amino acids, and the like. In fact, without being limited by theory, dihydroxyacetone is believed to provide an artificial tan to human skin by its reaction with the nitrogen containing proteins of the skin. See L. Goldman et al., "Investigative Studies with the Skin Coloring Agents Dihydroxyacetone and Glyoxal", The Journal of Investigative Dermatology, vol. 35, pp. 161-164 (1960); and E. Wittgenstein et al., "Reaction of Dihydroxyacetone (DHA) with Human Skin Callus and Amino Compounds", The Journal of Investigative Dermatology, vol. 36, pp. 283-286 (1961).
Currently available artificial tanning products have the disadvantage of not providing the desired control over color development of the tan. Artificial tans are often either too light or too dark, and tend to be too orange, uneven, or unnatural in appearance. Furthermore, artificial tans tend to take too long to develop, and once obtained, tend to fade too quickly and unevenly. Therefore, it would be highly desirable to provide dihydroxyacetone containing products which are chemically and physically stable, which are aesthetically pleasing, and which overcome these color development limitations.
A sun-tanned appearance is a symbol of a healthy, dynamic, and active life. Yet, the damaging effects of sunlight and artificial sources of ultraviolet radiation on the skin are well documented. Furthermore these effects are cumulative and potentially serious. These effects include erythema (i.e. sunburn), skin cancer, and premature aging of the skin. These adverse effects associated with exposure to ultraviolet radiation are more fully discussed in DeSimone, "Sunscreen and Suntan Products", Handbook of Nonprescription Drugs, 7th Ed., Chapter 26, pp. 499-511 (American Pharmaceutical Association, Washington, D.C.; 1982); Grove and Forbes, "A Method for Evaluating the Photoprotection Action of Sunscreen Agents Against UV-A Radiation", International Journal of Cosmetic Science, 4, pp. 15-24 (1982); and U.S. Pat. No. 4,387,089, DePolo, issued Jun. 7, 1983; the disclosures of all of which are incorporated herein by reference.
Sunscreens are the most common agents used for sun protection. However, sunscreens also have the disadvantage of preventing or greatly diminishing the cosmetically desirable tanning response. Thus, if an individual uses a sunscreen for protection from ultraviolet radiation, he or she is forced to forego a tanned appearance. Therefore, it would be highly desirable to provide protection from the harmful effects of ultraviolet radiation, and yet at the same time deliver a tanned appearance to the skin.
Furthermore, even if an individual is willing to accept the risks associated with exposure to ultraviolet radiation in order to obtain a tan, there are situations in which it may not be practical or even possible to do so because of time constraints, weather conditions, time of day, season of the year, geographic limitations, unavailability of an artificial ultraviolet radiation source, and the like. Therefore, it would be highly desirable to provide products that can deliver a tanned appearance whenever desired without the need for ultraviolet radiation.
Therefore, it would be highly desirable to provide a dihydroxyacetone containing emulsion for delivering both an artificial tan and also for providing protection from ultraviolet radiation. The combination of 3% dihydroxyacetone with 0.25% lawsone as a sunscreen active combination is described in the Federal Register, Vol. 43, No. 166, pp. 38206-38269, Aug. 25, 1978, this reference being incorporated herein by reference in its entirety. However, this combination is unsuitable for high SPF products. Furthermore, lawsone is a high melting bright yellow solid which is difficult to formulate and which is not readily available from suppliers in the United States. U.S. Pat. No. 3,177,120, to Black et al., issued Apr. 6, 1965 and U.S. Pat. No. 4,434,154, to McShane, issued Feb. 28, 1984 disclose dihydroxyacetone containing formulations which also incorporate a sunscreen. The '120 patent teaches compositions limited to the use of a single sunscreen not containing active amino groups (e.g., either homomenthyl salicylate or 2-ethoxyethyl p-methoxycinnamic acid); the '154 patent is limited to the use of octyl dimethyl PABA. However, homomenthyl salicylate is a very weak sunscreen unsuitable for use in products designed to deliver a high sun protection factor (i.e. SPF). Similarly, it is difficult to deliver high SPFs using either 2-ethoxyethyl p-methoxycinnamic acid or octyl dimethyl PABA, alone. Furthermore, due to growing consumer concerns over the use of PABA and PABA esters in sunscreen products, it would be preferable to develop dihydroxyacetone containing products which do not contain PABA and PABA derivatives. Therefore, the need exists for stabilized products which are effective for providing an artificial tan and which also provide adequate protection against ultraviolet radiation.
It is therefore an object of the present invention to provide emulsion compositions for imparting an artificial tan to human skin. Another object of the present invention is to provide emulsion compositions for imparting an artificial tan which exhibit a high degree of chemical and physical stability. A further object of the present invention is to provide stabilized emulsion compositions which are aesthetically appealing to consumers. A still further object of the present invention is to provide compositions for both imparting an artificial tan to human skin and also for protecting the skin from ultraviolet radiation. It is an even further object of the present invention is provide a method for artificially tanning human skin. It is another object of the present invention to provide a method for both artificially tanning human skin and for providing protection against ultraviolet radiation.
These and other objects of this invention will become apparent in light of the following disclosure.